WASHINGTON - Human activity such as driving and powering air conditionersis responsible for up to 60 percent of changes contributing to dwindling watersupplies in the arid and growing West, a new study finds.

Those changes are likely to accelerate, says the study published Thursdayin Science magazine, portending "a coming crisis in water supply for the westernUnited States."

The study is likely to add to urgent calls for action already coming fromWestern states competing for the precious resource to irrigate farms and quenchthe thirst of growing populations. Devastating wildfires, avalanches and droughthave also underscored the need.Researchers led by climate expert Tim P.Barnett at the Scripps Institution of Oceanography at the University ofCalifornia, San Diego, studied climate changes in the West between 1950-1999.They noted that winter precipitation falls …